Influenza, common cold – scientific based herbal alternatives

Interview with Prof. Dr. Stephan Pleschka (Germany) and Prof. Dr. Jim Hudson (Canada)


Echinacea purpurea

Influenza vaccines, antiviral medications, national and international pandemic plans - aren’t we already superbly equipped to deal with influenza threats of influenza pandemics or the seasonal influenza? Do we need alternatives?

J. Hudson Additional options for action are definitely desirable from the medical viewpoint. Simply to address more effectively the many individual problem cases, such as vaccinating pregnant women and children against influenza or drug intolerance and resistance. Especially for people unwilling to be vaccinated, there is currently a need for alternative approaches to provide protection against respiratory tract infections. Influenza vaccinations and the few antiviral agents with effects against influenza viruses are far from being optimal. This is why alternative options are urgently needed – something which has long been recognized by health authorities worldwide.

Why are extracts of medicinal plants, e.g. from the herb and roots of Echinacea purpurea, of such interest in this situation?

S. Pleschka Purple coneflower in particular has been found to have the ability to prevent common colds and influenzas and treat them in acute cases. Our latest research has now shown that this effect is attributable to an antiviral and anti-inflammatory effect. The traditional use of Echinacea purpurea to strengthen or balance the immune system is thereby substantiated by the latest findings.

What method do you use to demonstrate the antiviral effectiveness of a medicinal plant extract against viruses such as H3N2, H5N1, H1N1?

J. Hudson All studies of this kind start with cell cultures. These cultures were then infected with the relevant selected viruses, which were treated at different times and in different dosages with Echinacea extract. The results of the “plaque assay” then clearly show whether a plant extract can inhibit the infectiousness of the viruses. Further experiments are performed to find out whether or not viral resistance develops. This was of particular interest, since the treatment of influenza (e.g. by neuraminidase inhibitors) will inevitably lead to resistance. Finally, we attempt to establish how the observed antiviral effects can be explained at the molecular level.

Please summarize the results of your latest research.

S. Pleschka To treat the cell cultures, we used a standardized alcoholic extract of fresh herb (95%) and roots (5%) of Echinacea purpurea (L.) Moench (Echinaforce®, A. Vogel Bioforce AG, Switzerland). Five relevant influenza A strains were tested, including two classical human types, two highly pathogenic avian flu viruses with pandemic potential and the currently prevalent “swine flu virus”. Echinacea from a dose of 1.6 µg/ml onwards was already found to inhibit the infectiousness of the influenza viruses by more than 99%. This concentration is far below the local Echinacea dosage recommended for oral use. The virus-inhibiting effect was also maintained at high viral burdens.

How does this pronounced antiviral effectiveness come about?

J. Hudson All the studies we have conducted show that the Echinacea extract inhibits the surface protein of the influenza viruses – hemagglutinin – which they need to dock onto the body’s cells. As a result, the infection of the cells, the viral replication inside the cells and their further spread do not take place.

What other special properties does the extract have?

J. Hudson Whereas the influenza virus became resistant to a synthetic antiviral drug after a few treatment cycles, no such resistance developed during the Echinacea treatment. And even better: Echinacea was also able to inhibit the infectiousness of the virus that were already resistant to the chemical.

The discovery of the antiviral activity of Echinacea, especially against many typical common cold viruses, is mainly the result of your many years of research. How do you rate the discovery that Echinacea also has pronounced effects against influenza viruses?

S. Pleschka Since Echinacea is used mainly during the period between autumn and spring, experience reports and studies also invariably include seasonal influenza in January and February. To this extent, a direct activity against influenza viruses is certainly plausible.

Is a medicinal plant like Echinacea only a supplier of chemically defined substances, which after their scientific description, isolation and possible chemical modification can then be used medicinally?

J. Hudson An Echinacea fresh plant extract contains a broad range of different substances with different chemical structures. Based on existing knowledge, however, the antiviral, anti-inflammatory and antibacterial activities described may be attributable to different classes of active substances. Isolating an individual substance would always involve a reduction of the spectrum of action and would therefore be undesirable.
Moreover, organisms like viruses find it harder to develop resistance to a mixture containing a large number of substances than to a single chemical substance.

If Echinacea can build up a direct antiviral protective shield, e.g. after taking Echinaforce drops, doesn’t this effect remain confined to the oral cavity and pharyngeal space? Surely, an acute respiratory disease like swine flu also affects other parts of the body!?

S. Pleschka It is generally assumed that a large number of viruses that cause acute respiratory tract diseases initially infect in the posterior nasopharyngeal space. This applies both to the most common causative agents of common colds, the rhinoviruses, and to many influenza viruses, including the current swine flu viruses. Only after an infection has become established in this region do the viruses spread to the nose or deeper airways. The primarily infected pharyngeal space is thus certainly reached on oral use of Echinacea extract and the measured antiviral effects are related to the oral use of Echinacea.

No clinical studies are yet available for the infection inhibiting activity of Echinaforce in new influenza strains like swine flu virus. Do you nevertheless recommend its use for this condition?

J. Hudson We certainly still have a way to go before the effect against H1N1 viruses we have discussed will also be confirmed in clinical studies. However, we are already aware, from numerous studies, of the generally beneficial actions of Echinacea extract in influenza-like infections. And it is clear that these benefits derive both from longer-term immunmodulating effects and the normalization of pro-inflammatory signal substances that exacerbate symptoms. The antiviral component is a valuable addition to this multimodal spectrum of action. In our view, therefore, the use of Echinacea extract for prophylactic and therapeutic purposes can be recommended on the basis of existing knowledge. Especially since the medicinal plant extract Echinaforce is available over the counter without a prescription and is not affected by the distribution and rationing problems experienced with vaccines or synthetic drugs. Strengthening the body’s own immune response is certainly advantageous in such times.

Correspondence to:

Prof. Dr. Stephan Pleschka
Institut für Medizinische Virologie
Justus-Liebig Universität
Frankfurter Strasse 107
35392 Giessen – Germany
e-mail: [email protected]


Prof. Dr. James Hudson
Department of Pathology and Laboratory Medicine
University of British Columbia
2733 Heather Street
Vancouver V5Z 1M5 – Canada.
e-mail: [email protected]


© Bioforce AG, Switzerland, 2010

Professor Jim Hudson is considered to be one of the foremost virologists in Western Canada and is currently Professor Emeritus at the University of British Columbia. He has published over 130 papers in peer-reviewed journals and written a number of books, including “Antiviral Compounds from Plants”.
His research interests include elucidating the molecular mechanisms of action of herbal medicines and several collaborative projects with Institutes in developing countries in Africa and Asia.
Other key activities include naturally occurring phytomedicines as anti-viral and anti-microbial substances and how the appropriate use of herbal medicines can benefit human health.


© Pleschka, Germany, 2009

Professor Stephan Pleschka is a well-known virologist at the 400-years-old Justus Liebig-University in Giessen/Germany. Important scientific activities in virology and microbiology are:
* Identification, characterization and assessment of viral host factors which are relevant for both recognition and the targeted binding of influenza virus to host cells and for human infections.
* Relevance of viral and cellular factors and mechanisms regulating viral multiplication in infected cells and thus influence the viral replication.
* Viral spread and consecutive immune reactions of infected hosts including infection syndromes in different animal models.
In addition to his research in pathogenesis of influenza and new therapeutic approaches, other relevant work applies to biology of tumors, several lung diseases and the innate immunity.